Asset Impairment Expense (Impairment of Long-Lived Assets Held and Used by Asset) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Asset impairment expense			$ 1,096	$ 285	$ 91
DPL Subsidiary [Member]
Debt Instrument [Line Items]
Asset impairment expense	$ 624	$ 235	859	0	0
Kilroot [Member]
Debt Instrument [Line Items]
Asset impairment expense			0	121	0
buffalo gap III [Member]
Debt Instrument [Line Items]
Asset impairment expense			0	116	0
Ebute [Member]
Debt Instrument [Line Items]
Asset impairment expense			0	0	67
UK Wind (Newfield) [Member]
Debt Instrument [Line Items]
Asset impairment expense			0		12
UK Wind Development Projects [Domain]
Debt Instrument [Line Items]
Asset impairment expense				37
DP&L (East Bend)
Debt Instrument [Line Items]
Asset impairment expense			0	0	12
buffalo gap II [Member] [Member]
Debt Instrument [Line Items]
Asset impairment expense			159	0	0
Buffalo Gap I
Debt Instrument [Line Items]
Asset impairment expense			77	0	0
Other
Debt Instrument [Line Items]
Asset impairment expense			$ 1	$ 11	$ 0